1. Field of the Invention
The invention generally relates to circuits and in particular, to drive circuits for transistors.
2. Description of the Related Art
Power transistors are often used in switching applications, i.e., alternating between an xe2x80x9conxe2x80x9d state and an xe2x80x9coffxe2x80x9d state. For example, power transistors can be found in switching power supplies. These switching power supplies can be found in many different types of electronic equipment, such as power supplies for computers and telecommunications equipment. Other applications for switching power transistors include switching regulators, servos, motor controls, amplifiers, transmitters, and the like.
There are many types of power transistors. Examples include bipolar junction transistors (BJTs), metal oxide semiconductor field effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), and the like. A control input of a power transistor is coupled to a driver circuit, which drives the control input of the power transistor to achieve the desired xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d state. Desirably, a driver circuit for a device is matched to the input characteristics of the device.
A relatively new power transistor is a power junction field effect transistor (power JFET). However, power JFET devices pose certain challenges to driver circuits.
Embodiments of the invention include a driver circuit for a transistor, such as a power transistor. The driver circuit can turn the driven transistor on and off in response to a control signal. In an xe2x80x9conxe2x80x9d state, the driver circuit provides the input of the driven transistor with a positive bias. In an xe2x80x9coffxe2x80x9d state, the driver circuit provides the input of the driven transistor with a negative bias. The negative bias can be applied to transistors, such as to junction field effect transistors (JFETs), which use the negative bias to turn off. Advantageously, this negative bias can be optionally generated within the driver circuit without the need for a negative voltage supply or negative bias supplied to the driver circuit.